Level 2 Charging

I know I'm oversimplifying, but the car selects the charging rate it draws based on what the connector is telling it is supplying.
The easiest way to see is that it will take about a quarter of the time to charge. You can see on the screen what the 220v charging time is vs the 110v. That will be the most clear indicator.
Second your electric meter will spin a WHOLE lot faster.
There is no screen to select a charging rate with 220v, like there is with 110v. Its just not needed. It automatically goes to full charge rate.

The OnStar app will tell you. Go to "Vehicle Status", refresh and it will tell you plug-in voltage.

First thing first. Thank you both for the information. "Huey Driver" the time thing makes sense. I don't even want to look at electric meter RPMs. I kinda figured though the car would have had some info screen dedicated to 240 charging. "Bavarian13" I will definitely look at that next charge cycle. Thanks again!

A 240 charge will take about 4 hours, while a 120 12a charge will be twice as long

The 12 amp vs 8 amp thing is for 120V portable charger only, just like it says on the screen.

When 240V is supplied the charger negotiates with the car to determine what the max amperage it can supply will be.

For the ELR it will be 16 amps. 240V/16A is about 4 times the max rate of the portable charger can supply.